WebSub

WebSub is a publish/subscribe protocol, whereby a publisher posts resource updates to a channel on a hub and the hub subsequently relays those updates to channel subscribers. A repository could publish interactions that took place with its resources on a single channel, or on multiple channels, for example, one per type of activity (e.g. citation, review, annotating). This could be achieved in a manner similar to what is specified for ResourceSync Change Notifications. Aggregating applications could (selectively) subscribe to these repository channels. https://www.w3.org/TR/websub/